#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, l, r) for(int i = l; i <= r; i++)
#define FORD(i, l, r) for(int i = l; i >= r; i--)
#define all(x) (x).begin(), (x).end()
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
vector<pair<ll, ll>> a(n + 1);
FOR(i, 1, n) cin >> a[i].first >> a[i].second;
sort(a.begin() + 1, a.end());
vector<ll> pref(n + 1, 0);
FOR(i, 1, n) pref[i] = pref[i - 1] + a[i].second;
ll ans = 0, cand = 0;
FOR(r, 1, n){
ll cur_cand = a[r].first - pref[r - 1];
cand = max(cand, cur_cand);
ans = max(ans, pref[r] - a[r].first + cand);
}
cout << ans << "\n";
return 0;
}
